CHRONIC SODIUM BENZOATE THERAPY IN CHILDREN WITH INBORN-ERRORS OF UREA SYNTHESIS - EFFECT ON CARNITINE METABOLISM AND AMMONIA NITROGEN REMOVAL

Sodium benzoate (SE) therapy is known to increase ammonia (NH3) nitrog en elimination via conjugation with glycine and excretion as urinary h ippurate. In 16 children with inborn errors of urea synthesis we studi ed two issues: (1) the effect of chronic SE administration upon carnit ine metabolism and (2) the efficacy of chronic SE therapy as measured by the molar ratio of hippurate excretion to SE intake. Measurements w ere performed during elective hospitalizations when the patients were in stable metabolic condition. We found that chronic SE therapy is not associated with a constant level of hippurate elimination and that in terindividual and intraindividual variability may result in irregular removal of NH3 nitrogen. This variability may be due to various factor s including the formation of small quantities of benzoylcarnitine, whi ch was detected in the plasma of three of four patients receiving SE a nd carnitine therapy and in one of two patients on SE therapy without carnitine supplementation. The ratios of acyl to free carnitine were e levated in both plasma and urine in patients not receiving carnitine s upplementation, but were normal in patients receiving supplementation. (C) 1996 Academic Press, Inc.